Magnesium is the fourth most abundant cation in the human body—second most abundant in the intracellular environment—and takes part in more than three hundred enzymatic reactions. Magnesium is also essential for normal functioning of many of the body's organs, including the heart and kidneys. Magnesium deficiency is associated with an extensive list of diseases and conditions, including heart disease, arrhythmia, diabetes, migraine headaches, and osteoporosis. These conditions affect a tremendous number of people in the United States alone.
Unfortunately, many magnesium salts currently used to treat magnesium deficiencies orally, such as magnesium oxide, magnesium chloride, magnesium sulfate, magnesium gluconate or magnesium hydroxide, exhibit extremely low to moderate bioavailability, from about 2% for magnesium oxide to about 20% for magnesium chloride and magnesium gluconate. If a magnesium salt has a low bioavailability, very little, if any, magnesium will actually be absorbed into the body and reach the cells where the magnesium is needed. As such, it is desirable to have a highly bioavailable oral dosage form of magnesium that can be prescribed by physicians in dosages necessary to achieve normal intracellular magnesium levels, which are defined as a minimum concentration of 33.9 mEq/IU.
In order to prepare a solid oral dosage form containing one or more active ingredients (e.g., a magnesium salt), it is necessary that the material to be compressed into the dosage form possess certain physical characteristics which lend themselves to processing in such a manner. Among other things, the material to be compressed must be free flowing, must be lubricated, and, importantly, must possess sufficient cohesiveness to insure that the solid dosage form remains intact after compression. Magnesium salts (in particular, high bioavailability magnesium salts, including magnesium lactate), however, typically exhibit poor compressibility. Consequently, compressibility aids can be employed to impart cohesive properties to the drug(s) being formulated. The inclusion of compressibility aids, however, limits the dosage level that can be achieved in solid, oral dosage forms. As a result, oral dosage forms comprising a high loading of a high bioavailability magnesium salt are notoriously difficult to manufacture.
Even further, high-loading tablets typically lack a controlled release profile. That is, the inclusion of materials that can delay release of a drug from the tablet can limit the dosage level that can be achieved in solid, oral dosage forms. Consequently, oral dosage forms comprising a high loading of a magnesium salt are notoriously difficult to prepare in controlled release formulations.
This lack of satisfactory controlled release formulations further decreases the effectiveness of conventional magnesium oral dosage forms. More specifically, certain transient receptor potential (TRP) ion channels are located in the distal small intestines and are involved in regulation of magnesium reabsorption in the kidneys and absorption in the intestines. TRPM is a family of transient receptor potential ion channels that includes TRPM6 and TRPM7 (transient receptor potential cation channel, subfamily M (“melastatin”), members 6 and 7). Patients with deficient intracellular Mg2+ stores have higher uptake of Mg2+ via TPRM6/7 transports in the distal small intestine and higher Mg2+ reabsorption via TRPM6/7 transports in the distal convoluted tubule of the kidney resulting in less renal wasting of Mg2+, and greater transfer of blood Mg2+ into the intracellular compartment. Unfortunately, conventional magnesium oral dosage forms do not achieve satisfactory control of magnesium release to target this portion of the digestive tract; thus, optimal absorption is not achieved in magnesium deficient patients when using conventional formulations.
Because conventional processes for formulation of magnesium salts are unable to provide high bioavailability, high drug load, and controlled release characteristics in a single formulation, there remains a need for high-loading, controlled-release dosage forms for oral administration of highly bioavailable magnesium salts and methods for making and using same.